Last night I decided to do the old 25 cent trigger job on a couple of my Glocks. I did the G21 SF first and had no problems.

Next, I did the G17. I finish it up, and am testing it. I grab an empty magazine.. rack the slide.. it locks back properly. Seems fine. I grab a round and load it in to the magazine. I toss the magazine in.. rack the slide.. it tries to load the round but jams.

What the heck?

I clear it.. try again.. jams. Round wouldn't load in to the barrel. Very weird..

I tried a third time. Same result.

I disassemble the gun again... don't see anything wrong.. put it back togther. Try again.. jams.

Now I'm flustered. I put it down, and leave the room for a minute. Then it hits me...

I went back, took the round out of the magazine and inspected it.

Folks.. you can't load a .40 in to a 9mm.

(obviously the gun wasn't screwed up... )